"What they've decided to do, to me, is embarrassing," he said.
"I think when they got married, they married into royalty and they knew what they were getting themselves into - that's been Harry's life and Meghan's had a similar kind of life."
He added: "I think they've hurt the Queen, I think they've hurt the royals and it just doesn't work to be going to another country and serving England. It's never going to work."
"I'm a little embarrassed for them and I'm feeling very sorry for The Queen."
Thomas added that he has tried to get in touch through her mother Doria Ragland.
"I’ve spoken and sent letters to Doria [the mother of the Duchess of Sussex] to get to Meghan - and that hasn’t happened as well. So no, I’m at their mercy."
But he's also not backing down when it comes to testifying against his daughter as she sues the Mail On Sunday tabloid in the UK for publishing her private letters.
"I wish it hadn’t come to this, but I will certainly testify against the things that have been said about me. The lies," Thomas said.
"When me and Meghan end up in a courtroom together, it will be quite stunning for everybody."
He also said that "everything will come out" should he face Meghan in court.
And he blasted: "It will be emotional. I don’t know how we will both accept it.
"It would be the worst place to have to meet her and Harry — but it might come down to that because I will certainly testify against the things that have been said about me. The lies."